1. Field of the Invention
This invention relates to door exit devices in which a handle retracts upper and a lower vertical rods out of corresponding latch sockets in a door frame and pulls them into the door. More specifically, the invention relates to the latch mechanism which retains the vertical rods in the retracted position while the door is open to prevent inadvertent extension of the vertical rods and possible damage to the floor or ceiling as the door swings open.
2. Description of Related Art
Vertical rod door exit devices are widely used in schools, factories and commercial buildings, often in emergency exit applications. Devices of this type, have a handle, commonly a horizontal push bar or push plate, which moves in towards the door to retract an upper vertical rod from an upper socket in the door frame and a lower vertical rod from a socket in the floor. With the vertical rods retracted from their respective sockets, the door is free to swing open.
The horizontally operating handle of these devices provides simple and reliable door opening actuation, even in panic situations, and the vertical rods provide a connection between the door and the door frame which is highly resistant to forced entry.
In such devices, as the handle is operated, the vertical rods are retracted out of their respective sockets and into the door where a retraction latch mechanism operates to hold them in the retracted position until the door has been closed again. One problem with previous designs is that the latch mechanism occasionally fails to operate properly, or releases while the door is open. At such times, the vertical rods extend out from their retracted position and into contact with the floor or ceiling. This often results in damage if the door is moved while the rods are in contact with finished flooring or ceiling material.
Prior art vertical rod door exit devices have heretofore employed a latch mechanism which operates at a single preset retraction point. When the vertical rod to which the latch is attached is retracted to the specified point, the latch engages and prevents the rod from extending beyond this point until the door has been closed again. Closing the door operates a release on the latch and allows the vertical rods to extend into their sockets in the door frame.
In order to guarantee that the retraction latch will operate whenever the door is opened, the preset point could be set at the exact point where the vertical rods have been retracted just clear of their respective sockets. However, this "guaranteed operation point" setting would not normally provide sufficient clearance between the partially retracted rods and the flooring or ceiling material. Moreover, it would not be economically feasible to provide different latches, factory set to this point, or to individually adjust each latch in the field, as would be necessary to accommodate varying clearances between the door and door frames.
Accordingly, in all prior art vertical rod door exit devices, the retraction latch is factory set to operate beyond the guaranteed operation point discussed above, usually at a point close to the fully retracted position. In normal operation the vertical rods will almost always be pulled past the retraction latch actuation point, even with relatively light operating pressure on the handle. However, very occasionally the handle will be operated only partially, enough to withdraw the vertical rods from the sockets in the floor and ceiling and open the door, but insufficiently to retract the vertical rods to the retraction latch actuation point.
When this happens, the door is freed to swing open, but the rods are not latched and move into damaging contact with the floor or ceiling as soon as pressure is released from the handle. The result is usually an arc of damage on the flooring or ceiling material.
Bearing in mind these problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a latch mechanism which prevents the vertical rods from damaging the flooring or ceiling or from moving towards the extended position inadvertently.
Another object of the invention is to provide a latch mechanism for a vertical rod door exit device which always latches the vertical rods whenever the door is open.
A further object of the invention is to provide a latch mechanism which is capable of latching at all points along the retraction stroke of the vertical rod and which operates immediately to prevent any motion of the vertical rods towards the extended position once they have begun to move towards the retracted position.
It is another object of the present invention to provide a latch mechanism which is reliable and inexpensive to manufacture.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.